1. Field of the Invention
The present invention relates to a belt-driven conical-pulley transmission, such as a continuously variable transmission, having an endless torque-transmitting means in the form of a drive chain, as well as to a noise attenuation device for a shaft bearing supported in a bearing housing. The invention also relates to a cam ring structure for a noise attenuation arrangement.
2. Description of the Related Art
The requirement for comfort in automobiles is generally very high, also particularly with regard to acoustics. Especially for luxury automobiles, the driver and passengers wish to prevent any disturbing noise originating as a result of operation of the automobile power train. However, internal combustion engines and other power train components, such as transmissions, do create noises that can generally be perceived as constituting a disturbance. In continuously variable transmissions, the use of a plate-link chain can lead to the production of noise, because a plate-link chain, by virtue of its structure with links and pins, creates a repetitive knocking noise during operation of the transmission when the pins strike the conical disks of the transmission.
Belt-driven conical-pulley transmissions with a continuously variable transmission ratio include two pairs of conical disks located on shafts that are spaced from each other and around which an endless torque-transmitting means frictionally engages the conical surfaces of the pairs of conical disks. The transmission ratio of the transmission can be continuously modified by opposite changes of the spacings between the pairs of conical disks. Metallic chains are particularly used as endless torque-transmitting means in transmissions in which high torques can be transmitted, for example torque levels in the range of 300 Nm and higher.
Radially-undulating springs are currently used for vibration isolation of loaded rotation bearings. However, they have the disadvantage that as a result of their spring deflection, a displacement of the shaft as a function of the load is induced. That can lead on the one hand to loads that are so great as to damage components in contact with it, and on the other hand to an increase in noise production.
An additional disadvantage is the fact that the cam height on the inner radius and the perimeter of such radially-undulating springs are different. Manufacturing conditions result in tolerances. The addition of the tolerances is superimposed on the load-dependent displacement resulting from the spring deflection as a static positioning error, whereby the total tolerance in the position of the shaft relative to the housing becomes very large.
An object of the invention is the reduction of noise transmission, especially structure-borne noise transmission from the conical disks in a motor vehicle by the elimination of the load-dependent displacement of the shafts, while keeping the necessary manufacturing costs required for that purpose as low as possible.